Railway tie pads



March 31, 1959 FIG.3

E. SPQKES RAILWAY m: PADS Filed Dec. 23, 1955 WI II I .lm' mhlm.

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INVENTOR. RAY E. SPOKES B1 ATTORNEYS RAILWAY TIE PADS Ray E. Spokes, Ann Arbor, Mich, assignor to American Brake Shoe Company, New York, N.Y., a corporation of Delaware Application December 23, 1955, Serial No. 556,771

6 Claims. (Cl. 154-43) This invention relates to railroad tie pads and more particularly to coatings for such pads.

In my U.S. Patent No. 2,713,013, patented July 12, 1955, I have disclosed a railroad tie pad of composition material adapted to be arranged between the railroad tie and the tie plate used in anchoring the rail to the tie. The pad thus disclosed is of rectangular dimension and relatively thin in nature, and is composed of heavy duty, short length frictional cords and short pieces of frictioned fabric in a body of asphalt, frictioned by uncured rubber, latex or the like, such serving as a source of vulcanizable or curable material which when set during a high temperature cure of the pad bonds together in a unitary body the components of the pad.

As described in the aforesaid patent, the outer faces of the pad are advantageously coated with an asphalt material, which seals the pad against weather and penetration by foreign matter, and which also affords a soft facing adapted to flow in to the crevices of the railroad tie so as to in effect afford a grip between the pad and tie. It is therefore advantageous that these properties be assured at all times during normal life of the tie pad. In certain geographical locations, however, sub-zero temperatures of considerable duration prevail such that it becomes important that a composition railroad tie pad be capable of remaining flexible and adhesively related to the tie and tie plate under such severe low temperatures, and the primary object of the present invention is an asphaltic coating for a pad of the foregoing kind or kindred pad adapted to undergo cold flow and remain flexible at reduced temperatures to assure that the pad does not become embrittled, opening cracks that expose the body of the pad, and that the asphaltic coating on the pad remains capable of gripping the associated parts in the intended manner.

Specifically, it is the object of the present invention to afford an asphaltic coating for a pad of the foregoing kind consisting of a mixture of a relatively small amount of butyl rubber hydrocarbon and a relatively high proportion of asphalt, the asphalt in turn being a mixture of about equal parts by weight of low and high penetration asphalt.

Other and further objects of the present invention will be apparent from the following description and claims which, by way of illustration, set forth preferred embodi ments' of the present invention and the principle thereof and what I now consider to be the best mode in which I have contemplated applying that principle. Other embodiments of the invention embodying the same or equivalent principle may be used and changes may be made as desired by those skilled in the art without departing from the present invention.

In the drawings:

Fig. l is a top plan view of a tie pad;

Fig. 2 is a bottom plan view of a tie pad;

Fig. 3 is an end elevation of the pad; and

Fig. 4 is a front elevation of the pad.

Because of extremely low temperatures that prevail at times in some geographical areas, it is advantageous imite ta es. P e tl H 2,880,127 Patented Mar. 31, 1959- that a railroad tie pad such as the kind described in my aforesaid patent have a coating thereon which assures sustained flexibility of the pad and adhesive or non-slip qualities at unusually low temperatures.

Thus, it is advantageous that the outer faces of the pad TP be somewhat resilient and soft at all times so as to be capable of achieving a firm grip on the upper face of the railroad tie to resist the tendency for the pad to shift under load conditions and that the coating be conditioned against embrittlement to prevent cracking that would expose the pad to decay, water and abrasive matter. I have found that by incorporating a small amount of Butyl rubber into the asphalt coating, flexibility can be assured at sub-zero temperatures thereby preventing cracking of the tie pad due to embrittlement.

I have discovered that a maximum of about 2.5 to 3 percent by weight of Butyl rubber hydrocarbon is capable of imparting the desired amount of flexibility to the asphalt coating. Even this relatively small amount of Butyl rubber for maintaining flexibility has the tendency to reduce the tackiness or adhesiveness of ordinary asphalt having a melting point range of 170 to 200 F. and consequent low penetration characteristics, and accordingly it is necessary to use an appreciable amount of high penetration asphalt, that is, an asphalt having a penetration of 85 to 100, as will be described in more detail below, to overcome loss of tackiness due to Butyl rubber addition.

The high penetration asphalt is blended with about equal parts by weight of low penetration asphalt (penetration about 27) having a melting point of about 170 F The amount of high penetration asphalt is critical and must bemaintained within plus or minus 10 parts by weight of the desired equal parts by weight asphalt mixture. Thus, if more than about 60 parts by weight of high penetration asphalt is employed with less than about 40 parts by weight of low penetration asphalt, the resultant coating including the required amount of Butyl rubber is excessively tacky and displays an excessive amount of cold flow. Similarly, when less than about 40 parts by weight of high penetration asphalt are combined with more than about 60 parts by weight low penetration asphalt the reverse situation occurs, that is, there is not enough adhesiveness or cold flow present to achieve the desired grip on the tie and penetration of the crevices therein by the coating on the pad.

It has been found that the Butyl rubber hydrocarbon should not depart substantially from the 2.5 to 3 percent by weight ratio based on total weight of the coating. Thus, if only 2 percent by weight of Butyl rubber is employed, the desired amount of flexibility of the pad at low tem peratures is not achieved, and if the Butyl rubber appreciably exceeds 3 percent by weight the coating displays adhesiveness neither for wood nor steel. Attempts to overcome the latter effect by increasing the amount of high penetration asphalt produces a coating that tends to bleed, and thus it will be seen that in accordance with the present invention the amounts are critical within the ranges specified.

The following is an example:

Ingredient: Parts by weight Butyl rubber reclaim (20 percent pure hydrocarbon) 12.50

Low penetration asphalt melting point 170 F. 43.75 High penetration asphalt melting point The high penetration asphalt in the foregoing example, as mentioned above, imparts increased tackiness to the coating at ordinary temperatures that is not otherwise attainable in the presence of Butyl rubber. This particumasons? 3 lat asphalt has a penetration of 85-100 at 77 F. (100 gm. load, 5 seconds) and 30+ at 39.2 F. (200 gm. load, 60 seconds). The volatile content is less than one percent (evaporation at 325 F. for five hours), the asphaltene content is 43+ percent and the petrolene content is 56+ percent.

The low penetration or ordinary asphalt in the foregoing example has a penetration of 25-40 at 77 F. (100 gm. load, 5 seconds) and at 32 F. (200 gm. load, 60 seconds). The asphalteue content is 27+ percent, the petrolene content 72+ percent, and solubility in carbon tetrachloride is 99.5 percent.

It will be appreciated that the foregoing example is illustrative only of a preferred example, since variations within the ranges mentioned are possible. Thus, it will be observed that the pure butyl hydrocarbon content in the above example is 2.78 percent, and this may vary between about 2.5 and 3.0 percent.

To coat a tie pad as TP in accordance with the present invention, it is merely necessary to produce a hot melt of the composition and to dip the pad therein.

Reclaim Butyl rubber may be used as the source of pure Butyl rubber hydrocarbon, and the ordinary mineral filler content of the reclaim material is not a limitation to the use thereof as a source of Butyl rubber hydrocarbon for the present coating. Thus, in batch mixing it is convenient to prepare a master batch of forty percent Butyl reclaim rubber percent Butyl rubber hydrocarbon, 80 percent mineral filler) and sixty percent Venezuelan asphalt, melting point 170 F. A portion of the master batch may then be modified with the required amount of low melting point, high penetration asphalt as required for a particular application.

By Butyl rubber I mean copolymers of isobutylene and a small amount of a conjugated diolefin such as butadiene, isoprene or the like, characterized by a low degree of unsaturation as is well known in the art. An example is the copolyrnerization product of 98 percent isobutylene and 2 percent isoprene.

Hence, while I have illustrated and described the preferred embodiment of my invention, it is to be understood that this is capable of variation and modification.

I claim:

1. A railroad tie pad coating composition consisting essentially of a mixture of Butyl rubber hydrocarbon and asphalt in the ratio of about 2.5 to 3 parts by weight of Butyl rubber hydrocarbon, for preventing embrittlement of the pad at low temperatures, and about 97 to 97.5 parts by weight of asphalt, said asphalt being a blend of about equal parts by weight of low and high penetration asphalt, the high penetration asphalt maintaining adhesive, nonslip qualities for the pad at low temperatures, and the low penetration asphalt serving to prevent excessive cold flow of the coating due to high penetration asphalt.

2. A railroad tie pad coating composition consisting essentially of a mixture of Butyl rubber hydrocarbon and asphalt in the ratio of about 2.5 to 3 parts by weight of Butyl rubber hydrocarbon and about 97 to 97.5 parts by weight of asphalt, said asphalt being a blend of about equal parts by weight of low penetration asphalt, penetration about -40 at 77 F., and high penetration asphalt, penetration about 85-100 at 77 F.

3. In a railroad tie pad having a body composed of short length cords and small fabric pieces bonded together in to a unitary body by curable coatings thereon, and containing asphalt in the body thereof, an outer coating on the pad cosisting essentially of a mixture of Butyl rubber hydrocarbon and asphalt in the ratio of about 2.5 to 3 parts by weight of Butyl rubber hydrocarbon and about 97 to 97.5 parts by weight of asphalt, said asphalt being a blend of about equal parts by weight of low penetration asphalt, penetration about 25-40 to 77 F., and high penetration asphalt, penetration about -100 at 77 F.

4. In a railroad tie pad having a body composed of short length cords and small fabric pieces bonded together into a unitary body by curable coatings thereon, and containing asphalt in the body thereof, an outer coating on the pad consisting essentially of a mixture of Butyl rubber hydrocarbon and asphalt in the ratio of about 2.5 to 3 parts by weight of Butyl rubber hydrocarbon, for preventing embrittlement of the pad at low temperatures, and about 97 to 97.5 parts by weight of asphalt, said asphalt being a blend of about equal parts by weight of low and high penetration asphalt, the high penetration asphalt maintaining adhesive, non-slip qualities for the pad at low temperatures, and the low penetration asphalt serving to prevent excessive cold fiow of the coating due to the high penetration asphalt.

5. In a composition railroad tie pad, an outer coating on the pad and consisting essentially of a mixture of Butyl rubber hydrocarbon and asphalt in the ratio of about 2.5 to 3 parts by weight of Butyl rubber hydrocarbon and about 97 to 97.5 parts by weight of asphalt, said asphalt being a blend of about equal parts by weight of low and high penetration asphalt, said Butyl rubber hydrocarbon preventing embrittlement of the pad at low temperatures, the high penetration asphalt maintaining adhesive, non-slip qualities for the pad at low temperatures, and the low penetration asphalt serving to prevent excessive cold flow of the coating due to the high penetration asphalt.

6. In a composition railroad tie pad, a coating consisting essentially of a mixture of Butyl rubber hydrocarbon and asphalt in the ratio of about 2.5 to 3 parts by weight of Butylrubber hydrocarbon and about 97 to 97.5 parts by weight of asphalt, said asphalt being a blend of about equal parts by weight of low penetration asphalt, penetration about 25-40 at 77 F., and high penetration asphalt, penetration about 85-100 at 77 F.

References Cited in the file of this patent UNITED STATES PATENTS 2,431,386 Fischer Nov. 25, 1947 2,546,659 Sussenbach Mar. 27, 1951 2,578,001 Cubberley et al. Dec. 11, 1951 2,686,009 Crowe Aug. 10, 1954 2,688,005 Clayton et al. Aug. 31, 1954 2,690,418 Young Sept. 28, 1954 2,713,013 Spokes July 12, 1955 2,721,146 Hardman Oct. 18, 1955 2,728,734 Cubberley et al Dec. 27, 1955 2,770,421 Wilson Nov. 13, 1956 2,830,963 Traxler et al. Apr. 15, 1958 

1. A RAILROAD TIE PAD COATING COMPOSITION CONSISTING ESSENTIALLY OF A MIXTURE OF BUTYL RUBBER HYDROCARBON AND ASPHALT IN THE RATIO OF ABOUT 2,5 TO 3 PARTS BY WEIGHT OF BUTYL RUBBER HYDROCARBON, FOR PREVENTING EMBRITTLEMENT OF THE PAD AT LOW TEMPERATURES, AND ABOUT 97 TO 97.5 PARTS BY WEIGHT OF ASPHALT, SAID ASPHALT BEING A BLEND OF ABOUT 